Economics and improved cleaning make it desirable to clean food-processing equipment in place, without disassembly of the equipment, by circulating a cleaning solution through the equipment in a controlled manner. Often, plural cleaning solutions are used, in a controlled sequence. Although prior efforts have been made to clean rotary, centrifugal pumps without disassembly, those efforts have not been entirely satisfactory because those efforts have been characterized by low rates of cleaning solution flow. Frequently, extended cycles have been required for effective cleaning.
Conventionally, rotary pumps employ complex seals, in which the sealing face mating pressure is provided by a coiled spring. Typically, since such a seal must allow for slight movements to accommodate expansion, alignment, and wear, a movable seal, a movable shaft, or a movable member mounting the seal is required. Usually, in a food product pump, an O-ring also is required, which provides a seal between the spring-loaded seal and the pump shaft. The O-ring and associated recesses form a crevice that is difficult to clean, even under ideal conditions.
Positive-displacement pumps of current designs have seals, splined shafts, housings fitting tightly against lobar impellers, and, in some designs, nuts, all of which are in product zones with no provision for cleaning except through disassembly.
It would be highly desirable to provide improvements in rotary apparatus, particularly but not exclusively rotary, positive-displacement pumps and rotary, centrifugal pumps, whereby such apparatus could be effectively cleaned in place.